This invention pertains to the preparation of quinoline and aniline compounds from aromatic nitro compounds and ethylenically unsaturated hydrocarbons and more particularly to the use of catalysts based on Group VIII metal complexes which catalyze this reaction.
The synthesis of quinoline and derivatives thereof has long been of interest in the field of organic chemical synthesis because these compounds can be used for making dyes such as quinoline yellow, photosensitizing cyanine dyes, polymethine dyes and the like and pharmaceutical compounds, such as, antimalarials, local anesthetics, and amoebacides, and the like. Quinoline derivatives have also been used in the manufacture of mildew proofing agents, perfumes, and nicotinic acid.
One of the most well known methods for the preparation of quinoline is the Skraup synthesis which consists of heating a primary aromatic amine, such as, aniline with glycerol, concentrated sulphuric acid and an oxidizing agent such as nitrobenzene, ferric chloride or arsenic acid.
Another well known method is the Doebner-Miller synthesis which involves the interraction of a mole of an aromatic amine, such as, aniline with 2 moles of acetaldehyde in the presence of hydrochloric acid or zinc chloride to provide 2-methylquinoline.
The Conrad-Limpach-Knorr synthesis utilizes the condensation of a beta-keto ester, such as, ethyl acetoacetate with an aromatic amine, such as, aniline and affords 2- and 4-hydroxy quinolines.
The Pfitzinger reaction comprises the condensation of isatin with aldehydes, ketones, acids or esters to form 4-carboxy quinoline.
The Friedlander, Camps, and V. Niementokowski reactions condense an ortho-substituted aniline in a basic medium with a carbonyl compound to form the quinoline derivative.
Detailed reviews of procedures employed for the preparation of quinoline and its derivatives can be found in the Kirk-Othmer Encyclopedia of Chemical Technology, Second Edition, 1968, Vol. 16, pages 865-899, Interscience Publishers Incorporated, NYC, R. C. Elderfield's "Heterocyclic Compound", Volume 4, John Wylie and Sons, New York City--1952 and are set forth in Chemical Abstracts, Volume 52, 8140f (1958).